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Peter A. Smith, Leon N. McLin, David E. Kee, Brenda Novar, Paul Garcia; Laser induced fluorescence in the human lens. Journal of Vision 2005;5(8):462. doi: 10.1167/5.8.462.
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Purpose: When the human eye is exposed to a short-wavelength light in the near-ultra violet region, the light causes the lens to fluoresce, which produces a widespread glare effect on the retina. This glare may interfere with normal vision, especially at lower ambient illumination conditions. The aim of this study was to characterize the spatial extent of veiling glare caused by laser induced lens fluorescence.
Methods: The elevation in contrast threshold induced by eye-safe laser exposures from an ultraviolet laser operating at 364 nm was determined in human observers. The laser exposures were 8 mW·cm−2 at the cornea, and were 5 s in duration. The angle between the laser beam axis and the visual task was varied between at 2.5° and 30°. Contrast thresholds were determined by the method of adjustment for a Landolt ring target with a critical detail of 0.5° against a dim background (5 cd.m−2).
Results: The studies showed that a significant elevation in visual increment thresholds could be produced through ultraviolet laser induced lens fluorescence. Thresholds were increased by 50–100%, over a large part of the visual field. Thresholds for the target as far away as 30° from the laser beam axis were elevated by 50%. Equivalent background techniques estimated the luminance on the retina from the laser exposure to be around 5–10 cd·m−2,.
Conclusions: This study characterized the spatial extent of veiling glare caused by laser induced lens fluorescence and showed that exposure to a near-ultra violet laser at “safe” exposure levels (with respect to existing laser safety standards) can induce a veiling glare intense enough to impair visual performance.
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